The cosmic microwave background (CMB) is a faint radiation originating shortly after the Big Bang, detected uniformly across the sky. It is the oldest light we can observe and provides valuable insights into the early universe and its evolution. Detecting a specific pattern in this radiation, known as the B-mode of CMB polarization, would provide strong evidence for cosmic inflation —a very brief period of extremely rapid expansion in the very early universe— and would represent a major breakthrough in physics. For this reason, a large global effort is underway to search for the primordial polarization B-mode.
However, this signal is extremely weak and is obscured by the presence of contaminant emissions – known as foregrounds – arising from our own Galaxy and other astrophysical sources. Successfully detecting the primordial signal requires separating the true CMB from these contaminants, demanding precise knowledge of foregrounds, sophisticated component separation techniques, and realistic observational simulations. Moreover, beyond their role as contaminants, these foregrounds are highly valuable on their own, offering important information about a variety of astrophysical phenomena.
The RadioForegroundsPlus project addresses the challenge of cleaning CMB observations by delivering a state-of-the art description of the complex properties of foregrounds, developing advanced data analysis techniques, and producing templates and tools for generating realistic simulations. It focuses especially, although not exclusively, on Galactic radio foregrounds —including synchrotron, anomalous microwave emission (AME), and free-free— which dominate at the lower frequency range of CMB observations. It also aims to provide updated catalogues of extragalactic point sources (emission from other galaxies), study the Galactic magnetic field, and characterise the thermal dust emission that dominates at higher frequencies.
To achieve these goals, the project combines data from the European Planck satellite with three unique low frequency, ground-based experiments: QUIJOTE, C-BASS and S-PASS, making use of advanced data analysis techniques. These efforts are very relevant for preparing and supporting current and future CMB experiments (e.g. LiteBIRD, CMB-S4, Simons Observatory) and for forecasting their capability to detect B-mode polarization.
